Completion of a continuous zooplankton record for Windermere for the period 1979-2010, based upon data from >1300 archived samples. These data will allow us to detect changes in zooplankton abundance and composition in response to changes in fish predation and other environmental factors (Hypothesis 2)

980 individual fish, 250 zooplankton and 140 macroinvertebrate samples were analysed for their stable isotope composition over 27 years (1985-2011) to track changes in fish diet and food web structure of Windermere over the course of the roach expansion. These data will be used to assess the impact of increased fish abundance on the zooplankton population (Hypothesis 2), the link between the roach expansion on the decline in Arctic charr (Hypothesis 4), and the implications of these changes on pike, the top predator in the lake (Hypothesis 5).

Adult pike winter diet has been examined from Windermere over the last 34 years allowing us to address Hypothesis 5 with a complementary approach. The importance of the Arctic charr and brown trout have decreased, while that of the perch, pike and roach have increased, particularly markedly in the more eutrophicated South Basin. See Winfield et al 2012 below.

Application of a roach bioenergetics model to estimate changes in the predation pressure faced by zooplankton populations in Windermere, as a result of increasing fish abundances. Preliminary analyses suggest that, between 1991 and 2010, an effect of increasing fish predation upon copepod populations can be detected. The results of this work were presented at the SEFS8 international conference in July 2013. This work is now being developed, to examine impacts upon other zooplankton species.

Monthly hydroacoustic data from 1991 to 2010 have been analysed to determine the abundance of planktivorous fish and combined with individual consumption rates from the literature to estimate changes in overall fish predation pressure on zooplankton in the north basin (Hypothesis 2).

Monthly hydroacoustic data from 5 years between 2003 and 2010 and angler catches from 2005 to 2010 have been analysed to determine the open-water abundance and spatio-temporal patterns of large pike in the north and south basins (Hypothesis 5).